1. Field of the Invention
The present invention concerns a method of preparing a reversible electrical machine with a phase for starting a thermal engine of a vehicle.
The invention finds a particularly advantageous application in the field of the automobile industry, and more especially in that of vehicles equipped with an automatic starting/stopping system, such as the system known by the English term “Stop and Go”.
2. Description of the Related Art
Vehicles able to function according to the “Stop and Go” mode are equipped with a reversible electrical machine, or alternator/starter, coupled to the thermal engine, by means of a belt for example. In general terms, a reversible electrical machine of a vehicle combines two distinct functions, namely on the one hand the conventional function of alternator when the shaft of the thermal engine drives the rotor of the machine so as to produce an electric current at the stator, and on the other hand the starter function when conversely a current applied to the stator of the machine causes the rotor to rotate, which then drives the shaft of the thermal engine in a similar manner to a conventional starter.
The application of an alternator/starter to the “Stop and Go” operating mode consists, under certain conditions, of causing the complete stoppage of the thermal engine when the vehicle is itself at rest, and then restarting the thermal engine following, for example, an action by the driver interpreted as a restart request. A typical situation of “Stop and Go” is that of stopping at a red light. When the vehicle stops at the light, the thermal engine is automatically stopped and then, when the light goes green, the engine is restarted in particular by means of the alternator/starter following the detection by the vehicle starting control system of the pressing of clutch pedal by the driver or any other action that may be interpreted as the intention of the driver to restart his vehicle. The advantage of “Stop and Go” mode in terms of energy saving and pollution reduction, especially in an urban environment, will be understood.
When it is wished to start a thermal engine initially at rest by means of an alternator/starter, the first phase to be implemented is magnetizing the rotor by sending it a maximum excitation current. This magnetization, necessary for obtaining the required torque for starting the thermal engine, must last for a certain amount of time, around 150 ms, before the inverter is started up in order to make the rotor turn by applying an electric current to the stator of the machine.
This rotor preparation phase is executed on a start instruction sent by a control module responsible for managing the “Stop and Go” system, the starting being made effective by the excitation of the stator only after expiry of the magnetization period of approximately 150 ms.
This magnetization period therefore causes a routine delay in the starting of the thermal engine, prejudicial to the enjoyment and efficacy of driving when the automatic starting/stopping system of the vehicle is activated.